The present invention relates to methods and systems for producing thermal beacons in general, and to methods and systems for producing thermal marking signals, in particular.
Methods and devices for indicating the presence of an object in darkness (e.g., where darkness is defined as being outside the range of wavelengths invisible to the human eye) are known in the art. Infrared Radiation (IR) and Near Infrared Radiation (NIR) sources (beacons), mainly in the range of 0.7-1 micron are used in various applications as identification devices, for persons and vehicles. Near infrared light can be detected by special equipment which can translate the detected infra red image to a visible one. Different types of infrared beacons are known for use in covert security operations at night, where there is a need to be able to identify friend from foe or criminals from the police, animal watching, and the like.
These infrared beacons generally operate in the near IR range, and can be detected by image intensifiers, night vision goggles, black and white cameras, and the like. Black body Infrared beacons operating in the thermal region, such as mid-IR (3-5 micron) and long-IR (8-12 micron) are less prevalent. These infrared beacons generally employ a black body element, which is heated to a high temperature, and emits IR radiation in the thermal region. The blinking feature of the beacon is achieved by constantly rotating the black body element, or mechanically chopping the emitted radiation. Black body Infrared beacons can be detected by thermal cameras.
U.S. Pat. No. 4,912,224 to Andersen, entitled xe2x80x9cInfrared aircraft beacon lightxe2x80x9d, is directed to a near infrared aircraft lighting system for use on the exterior of aircraft in combination with an existing visible light beacon. The device includes a ring structure containing infrared source that is installed between a visible light beacon and the aircraft outer surface. The device enables pilots with night vision goggles to fly in formation, and see other aircrafts, which fly in their vicinity.
U.S. Pat. No. 5,804,829 to Palmer et al., entitled xe2x80x9cProgrammable infrared signal beaconxe2x80x9d, is directed to a near infrared signal beacon, which provides a visual location signal during poor light conditions. The device can be programmed to signal at least one of a plurality of coded messages, either in the visible light range of spectrum, or in the infrared range of the spectrum. The user of the beacon can select which of the plurality of flashing sequences will be transmitted by the light sources.
U.S. Pat. No. 5,225,828 to Walleston et al., entitled xe2x80x9cInfrared identification beaconxe2x80x9d, is directed to a device for alerting friendly personnel on land, sea or air. The beacon includes at least one near infrared light emitting diode and a visible light emitting diode, providing overlap conductive pole emanation of the NIR and visible light beams. The device can be steady or pulsed.
U.S. Pat. No. 5,414,405 to Hogg et al., entitled xe2x80x9cPersonnel identification devicexe2x80x9d, is directed to a device including a NIR LED contained within a housing. The device is adapted to be carried externally by a person or an object, such as vehicles, and enables, for example, to distinguish friend from foe in dark conditions. The housing possesses a xe2x80x9cstick-onxe2x80x9d capability, for example a Velcro or flexible magnetic strip on a base portion. The device is preferably adapted to flash, which enables the use of coded sequences of flashes.
U.S. Pat. No. 5,939,726 to Wood et al., entitled xe2x80x9cInfrared radiation sourcexe2x80x9d, is directed to a pulsable IR radiation source, which is intended for use in non-dispersive infrared gas analyzers. The device includes an emitting element, which is made of a narrow strip of foil. The emitting element is located in the hermetically sealed metal package with inert gas, such as nitrogen, helium or a combination thereof. The foil is heated by applying electrical power. The IR source provides high efficiency radiation at infrared wavelengths, and operates in the range of 1-3 Watts of power. The IR source cannot operate at high levels of power such as 10 Watts or more.
It is an object of the present invention to provide a method and a system for emitting pulsed infra red radiation, which overcomes the disadvantages of the prior art.
In accordance with the present invention, there is thus provided an emitter controller including a controller, and a power amplifier. The controller is connected to a power source. The power amplifier is connected to the controller, the power source and to an emitter. The controller provides a pulse sequence to the power amplifier for operating the emitter, and the controller determines the pulse sequence according to an available power voltage level.
In accordance with another aspect of the present invention, there is thus provided a method for operating an emitter controller. The method includes the steps of detecting a voltage level of a power signal, determining a heating time period, and producing a pulse signal. The power signal is provided to the emitter. The heating time period is determined according to the detected voltage level, and a target heating temperature. The pulse signal is produced according to the heating time period, for operating the power amplifier at the detected voltage level.